Hydrocarbon Processing - August 2022 - 38

Catalysts
FIG. 7. Static (A) and mobile (B) hoppers.
FIG. 8. Agglomerated catalyst.
FIG. 5. Sock loading.
proaches the height of the nozzle. This is
to avoid shadow effects in the dense-loaded
catalyst bed.
Before loading begins, a final inspection
of the reactor is required to ensure
that the reactor, the distribution and other
quench zone trays, and the catalyst support
grids are clean and free of any fouling
material that will affect liquid and gas distribution
across the reactor. The catalyst
dump nozzles are closed after the ceramic
plug and locking plate are installed.
The bed depth of the layers of ceramics
and catalyst is normally controlled by
a combination of markings on the reactor
wall and outage measurements to the ceramic/catalyst
bed surface, after ensuring
the bed is level. It is vital to confirm that
the minimum bed depths for ceramic
balls are adhered to, and a method to determine
if these layers are uniform (i.e., a
flat profile) should be used. This becomes
more important as the inside diameter of
the reactor increases. This guards against
catalyst migration and ensures good liquid
distribution during operation.
Equal preparation (or more) is
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AUGUST 2022 | HydrocarbonProcessing.com
FIG. 6. Dense loading.
quired on the ground as in the reactor(s)
for catalyst loading. Cranes must be located
so that each lift is simplified to ensure
that the catalyst supply to the top of
the reactor can keep up with the loading
rate of the dense-loading machine. Any
unplanned interruptions to dense loading
will affect the final loaded catalyst density.
Catalyst is delivered in catalyst bins,
bulk bags or drums. Ceramic balls and
catalyst should be brought to the site from
the warehouse in catalyst bed lots, and
catalyst bins/bags/drums must be clearly
marked with the catalyst name and size
to limit potential mistakes by loading the
wrong catalyst in the wrong bed.
A static hopper is installed above the
top reactor manway (FIG. 7A) to facilitate
catalyst delivery into the reactor. Catalyst
bins and bulk bags are the most efficient
means of storage and handling for catalyst
and can be lifted to the top of the reactor
to supply catalyst to the static hopper
and, from there, into the reactor. Catalyst
and ceramic balls delivered in drums or
small bags must be decanted into a mobile
hopper (FIG. 7B) for transporting between
the ground and the top of the reactor.
All hoppers should have coarse mesh
screens installed to avoid ingress of any
extraneous material or clumps of agglomerated
catalyst (FIG. 8) that may block the
loading pipe and dense-loading machine.
Setting up the static hopper, installing the
loading pipe, adjusting the scaffold platforms
and weather protection, and finally
setting up the dense-loading machine can
take several hours.
When loading ceramic balls into the
bottom of the reactor, avoid broken or
cracked balls in the region around and
on top of the outlet collector-the use of
spiral inserts, like those shown in FIG. 9, in
the top of the loading pipe or the use of a
proprietary loading systema
, for example,
is recommended.
Weather protection will be required
in most locations. Most catalysts, especially
hydrotreating catalysts, are sensitive
to moisture and must be protected from
any rain. The hoppers should have fitted
lids and the whole area around the reactor
manhole and the static hopper should
have weather protection. If a drum decanting
platform is being used on the ground,
it should have its own weather protection,
the same for all catalysts stored onsite
(bulk bags, drums or bins).
The fresh catalyst sampling protocol
must be clearly communicated to the
catalyst handling contractor and sample
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